Polymers having spiro orthoester groups, process of manufacturing and using

ABSTRACT

Process for the manufacture of polymers having repeating units comprising spiro orthoester groups of general formula (I), wherein A is C 1-6 -alkylene, C 1-6 -alkyleneoxycarbonyl or an oxygen-carbon bond, R 1  is hydrogen or methyl, R 2  is C 1-6 -alkyl or C 1-6 -alkyl substituted by C 1-6 -alkoxy or aryloxy, R 3  and R 4  independently are hydrogen or C 1-6 -alkyl, R 5  is hydrogen or methyl, R 6  is hydrogen, methyl, phenyl, carboxy, carboxy-C 1-6 -alkyl, carboxamido or cyano, n is an integer &gt;1 and m is 0 or an integer ≧1, with the proviso that the molecular weight of the polymer is between 500 and 1,000,000, the polymers obtained and their use specifically in dental filling materials.

This is a continuation of application Ser. No. 08/356,360, filed Dec.21, 1994 now abandoned.

DESCRIPTION

The subject matter of the present application is a process for themanufacture of polymers having repeating units comprising spiroorthoester groups, the polymers obtained thereby and their use for themanufacture of strain free composites, high strength adhesives,additives to other monomer mixtures to control the amount of shrinkageor expansion upon polymerization and specifically in dental fillingmaterials.

U.S. Pat. No. 4,387,215 already discloses that polymers formed by thepolymerization of polycyclic ring-opening monomers, such as monomerscomprising spiro orthoester groups, spiro orthocarbonate groups andpolycyclic ketal lactone groups show near zero shrinkage or expansionduring polymerization and are therefore usable for the manufacture ofstrain-free composites, high strength adhesive, precision castings andspecifically binders for propellants.

The subject matter of DE-A-24 8 597 is a method for the manufacture ofhomopolymers comprising spiro orthoester groups of the following formula

wherein R² is hydrogen or methyl and X is halogen.

Said homopolymers are stated to be useful as adhesives, casting resins,protection coatings and for dental materials. The homopolymers aremanufactured by the radical polymerization of2-halomethyl-8,8-dimethyl-9-(meth)acryloyloxy-1,4,6-trioxaspiro[4.4]nonanes. However, this process is not fullysatisfying with respect both to the manufacture of the startingmaterials and their polymerization.

The object of the present invention therefore is the provision of animproved process for the manufacture of polymers having repeating unitscomprising spiro orthoester groups which provides the products fromeasily available starting products with high purity and high yields,novel polymers obtained thereby and their use.

The subject matter of the present application therefore is the processaccording to claim 1. The subclaims comprise preferred embodiments ofthis process, novel polymers obtainable by this process and the use ofthese polymers.

The subject matter of the present invention therefore is a process forthe manufacture of polymers having repeating units comprising spiroorthoester groups of the following general formula I.

wherein

A is C₁₋₆-alkylene, C₁₋₆-alkyleneoxycarbonyl or an oxygen-carbon bond,

R¹ is hydrogen or methyl,

R² is C₁₋₆-alkyl or C₁₋₆-alkyl substituted by C₁₋₆-alkoxy or aryloxy,

R³ and R⁴ independently are hydrogen or C₁₋₆-alkyl,

R⁵ is hydrogen or methyl,

R⁶ is hydrogen, methyl, phenyl, carboxy, carboxy-C₁₋₆-alkyl, carboxamidoor cyano,

n is an integer >1 and

m is 0 or an integer ≧1, with the proviso that the molecular weight ofthe polymer is between 500 and 1,000,000,

which is characterized by reacting a polymer having repeating unitscomprising lactone groups of the following general formula II

wherein A, R¹, R³, R⁴, R⁵, R⁶, n and m are as defined above, with anoxirane compound of the following general formula III

wherein R² is as defined above.

According to a preferred embodiment A is a methylene group, an ethyleneoxycarbonyl group or an oxygen-carbon bond. R¹ preferably is methyl, R²preferably is C₁₋₆-alkyl substituted by phenoxy and more preferablyphenoxymethyl. R³ and R⁴ preferably are hydrogen or methyl. R⁵preferably is hydrogen or methyl. Preferably m is 0 and n is an integersuch that the molecular weight of the polymer is between 500 and500,000. more preferably between 1,000 and 50,000 and most preferablybetween 25,000 and 45,000.

According to a preferred embodiment of the process of the presentinvention the reaction is carried out in an organic solvent, such asbenzene, dichloromethane, trichloroethylene, dichloroethylene,carbontetrachloride, chlorobenzene, nitrobenzene and cyclohexane, morepreferably in anyone of the halogenated organic solvents inert to thereaction and most preferably in dichloromethane. The reaction of thestarting material of formula (II) with the oxirane compound of thegeneral formula (III) is preferably carried out in the presence of acatalyst or more preferably in the presence of a Lewis acid catalyst,such as boron trifluoride, boron trifluoride etherate, aluminumtrichloride, tin dichloride, tin tetrachloride, titanium tetrachlorideand iron trichloride. The reaction can be carried out at roomtemperature at a reaction time of 1 to 5 hours, preferably 2 to 4 hours.

According to a further preferred embodiment of the present invention,the starting compound of general formula (II) is manufactured by radicalpolymerization of a 2-oxo-tetrahydrofurane derivative of the followinggeneral formula (IV)

wherein A, R¹, R³ and R⁴ are as defined above. For the manufacture of acopolymer of the above formula (I), wherein m is an integer of ≧1, thepolymerization is carried out in the presence of a copolymerizablemonomer of the following general formula (V)

wherein R⁵ and R⁶ are as defined above. Specifically preferredcopolymerizable monomers of formula (V) are ethylene, propylene,(meth)acrylic acid and the esters thereof, acrylonitrile, acrylamide,styrene and the like.

The polymerization yielding the starting compounds of formula (II) ispreferably carried out in solution in an inert organic solvent and inthe presence of a radical forming catalyst. As the organic solventpreferably an aromatic solvent, such as toluene is used. As the catalysta free radical forming catalyst useful for such polymerizations can beused, such as a peroxide catalyst or more preferablyazobisisobutyronitrile.

The subject matter of the present application further are polymershaving repeating units comprising spiro orthoester groups of thefollowing general formula (I)

wherein A, R¹, R², R³, R⁴, R⁵, R⁶, m and n are as defined above.Specifically preferred polymers are homopolymers having repeating unitscomprising spiro orthoester groups of the following general formula VI

wherein

A is C₁₋₆-alkylene. C₁₋₆-alkyleneoxycarbonyl or an oxygen-carbon bond,

R¹ is hydrogen or methyl.

R³ and R⁴ independently are hydrogen or C₁₋₆-alkyl,

n is an Integer ≧1 with the proviso that the molecular weight of thepolymer is between 3,000 and 50,000.

The process of the present invention is specifically advantageous, inthat the polymers having useful properties are easy to synthesize fromreadily available starting material and provides the products with highyield and high purity. The 2-oxo-tetrahydrofurane derivatives of thefollowing general formula (IV)

wherein A, R¹, R³ and R⁴ are as defined above, can be manufactured withease by reacting the corresponding lactone of formula (VI)

with (meth)acryloyl chloride.

Specifically preferred polymers corresponding to the above generalformula (I) are the following:

Homopolymers having repeating units comprising spiro orthoester groupsof the following general formula VI

wherein

A is C₁₋₆-alkylene. C₁₋₆-alkyleneoxycarbonyl or an oxygen-carbon bond,

R¹ is hydrogen or methyl,

R³ and R⁴ independently are hydrogen or C₁₋₆-alkyl,

n is an integer >1 with the proviso that the molecular weight of thepolymer is between 3,000 and 50,000.

poly-{1-methyl-1-[2-(phenoxymethyl)-1,4,6-trioxaspiro[4.4]nonane-7-yl]methoxycarbonyl]ethylenes} having theformula 4

 and a molecular weight in the range of 5,000 to 500,000, preferably20,000 to 40,000.

poly-{1-methyl-1-[2-(phenoxymethyl)-1,4,6-trioxaspiro[4.4]nonane-7-yl]carbonyloxy-ethoxycarbonyl]ethylenes}having the formula 8

 and a molecular weight in the range of 5,000 to 50,000, and

poly-{1-methyl-1-[2-(phenoxymethyl)-8,8-dimethyl-1,4,6-trioxaspiro[4.4]nonane-9-yl]oxycarbonyl]ethylenes}having the formula 12

 and a molecular weight in the range of 5,000 to 500,000, preferably20,000 to 40,000.

The above homopolymers preferably have a molecular weight in the rangeof 5,000 to 50,000, more preferably between 10,000 and 40,000 and evenmore preferred between 25,000 and 35,000.

The polymers of the present invention comprise pending spiro orthoestergroups, which can be subjected to ring opening polymerization. As isknown from U.S. Pat. No. 4,387,215, this ring-opening polymerization hasthe effect that the polymer does in contrast to normal polymerizationnot show shrinkage but no shrinkage or even slight expansion caused bythe ring opening, as can be demonstrated by the following scheme,showing that in dependency from the attack of the electrophilic agent atthe 0-1 atom or 0-4 atom two different polymer structures are obtained:

Therefore, the polymers of the present invention are highlyadvantageous, in that they can be used to provide strain free hardenablecompositions providing hardened products, which have a controlled amountof shrinkage or expansion, an effect very desirable for example indental filling compositions, which should most closely fit to the toothto be restored.

The properties of the polymers of the present invention can becontrolled as desired by the proper selection of the pending spiroorthoester groups and the fact as to whether copolymerizable monomersare present and what kind of copolymerizable monomers they are. On thebasis of these copolymerizable monomers further properties of thecorresponding copolymers can be provided.

The preferred homopolymers of the present invention can be used as suchor blended with other polymers, fillers, reinforcing fibers andadditives usual for the manufacture of composites and casting resins andspecifically dental filling compositions. Therefore, the presentinvention provides for the possibility of tailoring the polymersaccording to the desired properties of the final hardened product.

A further subject matter of the present invention therefore is the useof the above polymers which are capable of expanding upon reaction ofthe spiro orthoester groups for the manufacture of strain freecomposites, high strength adhesives, as additives to other monomermixtures to control the amount of shrinkage or expansion uponpolymerization and specifically for the manufacture of dental fillingmaterials. For this type of utility, the polymers of the presentinvention are mixed with usual fillers, pigments, hardeners and usualadditives.

During their use the polymers of the present invention are subjected toa ring opening polymerization providing the expansion of the polymer.This polymerization is preferably initiated by catalysts which generatecations during radiation. As such catalysts diaryliodonium salts,organometallic salts, such as(β⁵-2,4-cyclopentadiene-1-yl)[(1,2,3,4,5,6-β)-(1-methylethyl)-benzene]-iron(I)hexyfluorophosphateand triarylsulfonium salts may be used. These catalysts are mixed withpolymers and additional components, such as pigments, fillers and etc.,brought to the desired shape, such as the filling of a cavity in atooth, and are then subjected to the ring opening polymerization byirradiation with actinic light, such as ultraviolet light.

The present invention can be explained more in detail by makingreference to the following examples.

EXAMPLE 1

Poly-{1-methyl-1-[2-(phenoxymethyl)-1,4,6-trioxaspiro[4.4]nonane-7-yl]methoxycarbonyl]ethylene}

a) synthesis of 5-(methacryloyloxymethyl)-2-oxo-tetrahydrofurane (2)

 5-Hydroxymethyl-2-oxo-tetrahydrofurane (1) was obtained according tothe method of R. M. Silverstein (Tetrahedron, 34. (1978) 1449). To thealcohol (10.1 g, 87 mmol) were added 100 ml dichloromethane and 8.4 ml(104 mmol) pyridine; the mixture was cooled to −10° C. Then a solutionof 40 ml dichloromethane and 8.3 ml (87 mmol) methacryloyl chloride wereadded dropwise during a period of 1.5 h. The solution was stirredovernight at room temperature. The solvent was evaporated and theresidue was chromatographed on silica gel (ethylacetate/hexane (2:1)).

Yield: 13.4 g =83.5 %

IR-spectrum: (ν cm⁻¹, KBr) 2959 (CH₃); 2934 (CH₂); 1779 (C═O, lactone);1720 (C═O); 1637 (C═C); 1153 (C—O); 1074 (C—O—C); 886 (═CH₂).

¹H-NMR-spectrum: (δ in ppm, 200 MHz, CDCl₃) 6.14 (m, 1H,═CH₂ cis); 5.63(m, 1H═CH₂ trans), 4.8 (m, 1H, CH); 4.32 (d/d, 2H, CH₂O); 2.61 (m, 2H,CH₂); 2.39 (m, 2H, CH₂); 1.95 (t, 3H, CH₃).

¹³C-NMR-spectrum: (δ in ppm, 50.3 MHz, CDCl₃) 176.4 (C═O, lactone);166.7 (C═O); 135.5 (C—CH₃); 126.3 (═CH₂); 77.2 (CH₂—O); 65.4 (O—CH—CH₂);28.0 (C⁶⁷); 23.8 (Cβ); 16.1 (CH₃).

b) Radical polymerization of5-(methacryloyloxymethyl)-2-oxo-tetrahydrofurane (2)

To a solution of 1.8 g (9.7 mmol)5-(methacryloyloxymethyl)-2-oxo-tetrahydrofurane (2) were added 40 mltoluene and 15.9 mg (1 mol %) azobisisobutyronitrile (AIBN). The mixturewas heated to 70° C. on an oil bath for 20 h and then the solvent wasevaporated. The oily product was dissolved in 5 ml dichloromethane andprecipitated in hexane. The colorless polymer was filtered and dried invacuo.

Yield: 1.66 g=92%.

IR-spectrum: (ν In cm⁻¹, KBr) 2955 (CH₃); 1778 (C═O, lactone); 1731(C═O); 1156 (C—O); 1071 (C—O—C).

¹H-NMR-spectrum: (δ in ppm, 200 MHz, DMSO-d₆, T=100° C.) 4.9-4.65 (m,1H, CH); 4.3-3.9 (m, 2H, CH₂O); 2.64-2.23 (m, 4H, CH₂); 2.18-1.68 (m,2H, CH₂—CCH₃); 1.18-0.75 (s, 3H, CH₃).

¹³C-NMR-spectrum: (δ in ppm, 50.3 MHz, DMSO-d₆, T=100° C.) 175.8 (C═O,lactone): 175.2 (C═O); 76.2 (CH₂-O); 65.6 (C⁶⁵); 44.1 (C—CH₃); 27.1(C^(α)); 22.9 (C^(β)); 16.1, 16.7 (CH₂—C—CH₃).

c) Synthesis of polyl{1-methyl- 1[2-(phenoxymethyl)-1,4,6-trioxaspiro[14.4]nonane-7-yl]methyloxycarbonyl}ethylene (4) via polymer analogousreaction

To a solution of 1.4 g (7.4 mmol)polyl{-methyl-1[(2-oxo-tetrahydrofurane-5-yl)methyloxycarbonyl]}ethylene(3) were added 80 ml dichloromethane, 4 ml (30 mmol)2,3-epoxypropylphenylether and 0.15 ml borontrifluoride etherate. Themixture was stirred at room temperature for 4 h, and the catalysthydrolized with 5 ml aqueous sodium hydroxide, the organic layer wasseparated, dried and concentrated and the polymer precipitated bypouring the solution in ethanol.

IR-spectrum: (ν in cm⁻¹, KBr) 3032 (CH, arom.); 2944 (CH₃); 1779 (C═O,lactone); 1732 (C═O); 1599 (C—C, arom.); 1152 (C—O—C): 756 (CH, arom.).692 (CH, arom.).

¹H-NMR-spectrum: (δ in ppm, 200 MHz, CDCl₃) 7.36-7.08 (m, 2H, H arom.);7.00-6.71 (m, 3H, H arom.); 4.86-4.45 (m, 1H) 4.27-4.09 (m, 2H,CH₂—O—C═O); 4.09-3.09 (m, 5H, CH, CH₂); 2.64-1.64 (m, 4H, CH₂);1.45-1.16 (m, 2H, CH₂—CCH₃), 1.16-0.68 (m, 3H, CH₃).

EXAMPLE 2

Poly-{1-methyl-1-[2-(phenoxymethyl)-1,4,6-trioxaspiro[4.4]nonane-7-yl]carbonyloxy-ethoxycarbonyl]ethylene}

a) Synthesis of 5-{[2-(methacryloyloxy)ethyloxy]carbonyl}-2-oxo-tetrahydrofurane

The starting carboxylic acid (5) was synthesized according to the methodof C. Herdeis (Synthesis, 232 (1986)). 6.5 g (50 mmol) of the carboxylicacid (5) were dissolved in 300 ml dichloromethane and cooled to −10° C.To the solution were added 11.4 g (55 mmol) dicyclohexylcarbodiimide,6.7 ml (55 mmol) hydromethylmethacrylate and 0.61 g (5 mmol)N,N′-dimethylamino pyridine (DMAP). The mixture was stirred overnight,the dicyclohexylurea filtered off and the resulting filtrate extractedwith water (3 times), acetic acid and again with water. The organiclayer was dried with Na₂SO₄ and the solvent evaporated. The solid waschromatographed on silica gel (dichloromethane/ethylacetate (9:1).

Yield: 10.8 g=89.2%

IR-spectrum: (ν in cm⁻¹, KBr) 2968 (CH₃); 1789 (C═O, lactone); 1748(C═O); 1631 (C═C); 1154 (C—O); 1064 (C—O—C).

¹H-NMR-spectrum: (δ in ppm, 90 MHz, CDCl₃) 6.15 (s, 1H,═CH₂); 5.6 (m,1H,═CH₂); 4.95 (m, 1H, CH—O): 4.4 (s, 4H, CH₂—O); 2.6 (m, 4H, CH₂); 1.95(s, 3H, CH₃).

¹³C-NMR-spectrum: (δ in ppm, 50.3 MHz, CDCl₃) 175.8 (C═O, lactone);169.6 (C═O); 165.6 (C═O); 131.5 (CH═CH₂); 127.6 (═CH₂); 75.4 (CH); 63.3(CH₂—O); 61.6 (CH₂—O); 26.5 (CH₂); 25.6 (CH₂); 16.1 (CH₃).

b) Polymerization of5-{[2-methacryloyloxy)ethyloxy]carbonyl}-2-oxo-tetrahydrofurane (6)

To a solution of 1.4 g (5.8 mmol) of (6) were added 50 ml toluene and0.95 mg (0.1 mol %) AIBN. The mixture was heated to 80° C. on an oilbath for 24 h. The solvent was removed under reduced pressure, theproduct dissolved in 5 ml dichloromethane and precipitated in hexane.The polymer was filtered and dried in vacuo.

Yield: 1.25 g=89.3%

IR-spectrum: (ν in ppm, KBr) 2966 (CH₃); 1790 (C═O, lactone); 1706(C═O); 1694 (C═O); 1145 (C—O); 1061 (C—O—C)

¹H-NMR-spectrum: (δ in ppm, 200 MHz, DMSO-d₆) 5.35 (m, 1H, C^(γ)H); 3.7(m, 4H, O—CH₂—CH₂—O); 2.6-2.36 (m, 2H, C^(α)H₂); 2.36-1.86 (m, 2H,CH^(β)H); 1.86-1.45 (m, 2H, CH₂); 1.2 (m, 3H, CH₃).

¹³C-NMR-spectrum: (δ in ppm, 75.4 MHz, DMSO-d₆) 176.33 (C═O, lactone);175.31 (C═O, ester); 169.7 (C═O, ester); 75.9 (CH); 62.58 (d,CH₂—CH₂—O);44.37 (CH₂—C(CH₃)); 44.05 (C(CH₃)); 26.4 (CH₂); 25.15 (CH₂); 18.06(CH₃).

c) Polymer analogous reaction of5-{1-methyl-1-[2-(2-oxo-tetrahydrofurane-2-yl)carbonyloxy]ethyloxycarbonyl}ethylene(7) with 2,3-epoxypropylphenylether

To a solution of 0.75 g (3.1 mmol) poly{1-methyl-1[2-(5-oxotetrahydrofurane-2-yl)carbonyloxy]ethyloxycarbonyl}ethylene (7)was added 60 ml dichloromethane, 1.7 ml (12.4 mmol)2,3-epoxypropylphenylether and 0.15 ml borontrifluoride etherate. Themixture was stirred at room temperature for 4 h, the catalyst hydrolizedwith 5 ml of aqueous sodium hydroxide. The organic layer was separated,dried, concentrated and the polymer was precipitated by pouring thesolution in ethanol.

IR-spectrum (ν in cm⁻¹, KBr) 3031 (CH,arom.); 2944 (CH₃); 1779 (C═O,lactone); 1706 (C═O); 1693 (C═O); 1599 (C—C arom.); 1152 (C—O—C); 756(CH, arom.); 692 (CH, arom.).

¹H-NMR-spectrum: (δ in ppm, 200 MHz, CDCl₃) 7.3 (m, 2H, H arom.); 6.9(m, 3H, H arom.); 4.3-3.7 (m, 10H, CH₂O); 2.23-1.84 (m, 4H, CH₂); 1.27(m, 2H, CH₂—CCH₃); 0.9 (m, 3H, CH₃).

EXAMPLE 3

Poly-{1-methyl-1-[2-(phenoxymethyl)-8,8-dimethyl-1,4,6-trioxaspiro[4.4]nonane-9-yl]oxycarbonyl]ethylene}

a) Synthesis of 4,4-Dimethyl-3-methacryloyloxy-2-oxo-tetrahydrofurane(10)

8.2 g 4,4-Dimethyl-3-hydroxy-2-oxo-tetrahydrofurane (9), 10.45 mltriethylamine (NEt₃),0.77 g 4-dimethylamino-pyridine (DMAP) weredissolved in 120 ml dichloromethane. At 0° C. 6.02 ml methacryloylchloride were added dropwise and stirred for 3 h. After filtration thereaction mixture was extracted with saturated sodium hydrogen carbonate,potassium hydrogen sulfate and saturated sodium chloride, dried(Na₂SO₄), filtered and concentrated by solvent removal under reducedpressure. The obtained pale yellow product was purified by columnchromatography on silica-gel 60 (Merck, 70-230 mesh), elution withdichloromethane/ethylacetate (9:1).

Yield: 8.32 g,≈66.6 %

¹H-NMR-spectrum (CDCl₃): δ=1.2 (—C(CH₃)₂₋, 2s,6H); 2.0 (—CH₃, s, 3H);4.1 (—CH₂, s, 2H); 5.45 (—CH—, s, 1H); 5.7 (=CH, m, 1H), 6.25 (=CH, m,1H)

IR-spectrum (KBr) (ν in cm ⁻¹); 3108 (w, s,═CH); 2970-2880 (s, aliphat,CH), 1792 (s, s, O—C═O, lactone); 1727 (s, s, C═O); 1638 (s, s, C═C);1350-1050 (s, C—O—C).

b) Poly-[4,4-dimethyl-3-methacryloyloxy-2-oxo-tetrahydrofurane] (11)

1.5 g of 4,4-dimethyl-3-methacryloyloxy-2-oxo-tetrahydrofurane (10) and6.2 mg azoblsisobutyronitrile (AIBN) were dissolved in 75 ml THF andheated to 80° C. The polymerization was carried out for 24 h in aconstant temperature bath. The polymer was precipitated in hexane.

The molecular weight of polymer (11) determined by gel-permeationchromatography was M_(W)=18000.

Yield: 1.08 g=72% polymer 0.35 g=23 % oligomers

¹H-NMR-spectrum (CDCl₃): d=1.2 (m, CH₃, 9H); 2.11 (m, CH₂, 2H); 4.03 (s,CH₂O, 2H); 5.28 (s, OCHC═O, 1 H)

IR-spectrum (KBr), (ν in cm⁻¹): 2970-2880 (s, aliphat, CH); 1794 (s, s,O—C═O, lactone); 1741 (s, s, C═O); 1350-1050 (s, C—O—C).

c) Polymer analogous reaction of (II) with phenoxymethyloxirane

1.5 g poly(4,4-dimethyl-3-methacryloyloxy-2-oxo-tetrahydrofurane) (11)and 4.1 ml phenoxymethyloxirane were dissolved in 60 ml dichloromethane.0.15 ml boron trifluoride etherate were added and the reaction mixturewas stirred for 3 h. The mixture was extracted with sodium hydroxide andthe organic layer was dried with Na₂SO₄ and evaporated. The polymer wasprecipitated in hexane.

The molecular weight of polymer (12) determined by gel-permeationchromatography was M_(W)=35000.

Yield: 1.81 g

¹H-NMR-spectrum (DMSO-d₆)δ: 1.2 (m, CH₃, 9H); 2.1 (m, CH₂, 2H); 3.3-5.4(m, CH₂, CH, 8H); 6.9 (m, C₆H₅, 3H); 7.2 (m, C₆H₅, 2H).

IR-spectrum (KBr) (ν in cm⁻¹): 3060, 3039 (w, ═C—H); 2967-2878 (s,aliphat, C—H); 1794 (s, s, O—C═O, lactone); 1738 (s, s, C═O): 1600 (s,s, arC—C); 1350-1050 (s, C—O—C); 756, 692 (s, s, arC—H).

¹H-NMR spectra were recorded on a CXP -200 FT-NMR and the IR-spectra ona FTIR 60 SRX-spectrometer.

Gel-permeation chromatography analysis were carried out using a Watersapparatus with UV-detector and a Melz apparatus to detect the refractiveindex.

Molecular weights were determined by gel-permeation chromatography usingTHF as eluent and calibration with PMMA standards.

What is claimed is:
 1. A process for the manufacture of polymers havingrepeating units comprising spiro orthoester groups of the followinggeneral formula I

wherein A is C₁₋₆-alkylene, C,₁₋₆-alkyleneoxycarbonyl or anoxygen-carbon bond, R¹ is hydrogen or methyl, R² is C₁₋₆-alkyl orC₁₋₆-alkyl substituted by C₁₋₆-alkoxy or aryloxy, R³ and R⁴independently are hydrogen or C₁₋₆-alkyl, R⁵ is hydrogen or methyl, R⁶is hydrogen, methyl, phenyl, carboxy, carboxy-C₁₋₆-alkyl, carboxamido orcyano, n is an integer >1 and m is 0 or an integer >1, with the provisothat the weight average molecular weight of the polymer is between 500and 1,000,000 as measured by gel-permeation chromatography, the processcomprising reacting a polymer having repeating units comprising lactonegroups of the following general formula II

wherein A, R¹, R³, R⁴, R⁵, R⁶, n and m are as defined above, with anoxirane compound of the following general formula III

wherein R² is as defined above.
 2. The process according to claim 1,wherein the reaction is carried out in a polar organic solvent and inthe presence of a catalyst.
 3. The process according to claim 2, whereinthe reaction is carried out in a halogenated organic solvent and in thepresence of a Lewis acid catalyst.
 4. The process according to claim 3,wherein the reaction is carried out in dichloromethane and in thepresence of borontrifluoride etherate as the catalyst.
 5. The processaccording to claim 1, wherein the reaction is carried out at roomtemperature.
 6. The process according to claim 1, wherein the startingcompound of general formula II is manufactured by radical polymerizationof a 2-oxo-tetrahydrofurane derivative of the following general formulaIV

wherein A, R¹, R³ and R⁴ are as defined in claim 1, optionally in thepresence of a copolymerizable monomer of the general formula V

wherein R5 and R⁶ are as defined in claim
 1. 7. The process according toclaim 6, wherein the polymerization is carried out in solution in aninert organic solvent and in presence of a radical forming catalyst. 8.The process according to claim 7, wherein the solvent comprises anaromatic solvent and the catalyst comprises a peroxide catalyst orazobisisobuytronitrile.
 9. A polymer having repeating units comprisingspiro orthoester groups of the following general formula I

wherein A is C₁₋₆-alkylene C₁₋₆-alkyleneoxycarbonyl or an oxygen carbonbond, R¹ is hydrogen or methyl, R² is C₁₋₆-alkyl or C₁₋₆-alkylsubstituted by C₁₋₆-alkoxy or aryloxy, R³ and R⁴ independently arehydrogen or C¹⁻⁶-alkyl, R⁵ is hydrogen or methyl, R⁶ is hydrogen,methyl, phenyl, carboxy, carboxy-C₁₋₆-alkyl, carboxamido or cyano, n isan integer >1 and m is 0 or an integer>1, with the proviso that theweight average molecular weight of the polymer is between 500 and1,000,000 as measured by gel-permeation chromatography.
 10. Ahomopolymer having repeating units comprising spiro orthoester groups ofthe following general formula VI

wherein A is C₁₋₆-alkylene, C₁₋₆-alkyleneoxycarbonyl or an oxygen-carbonbond, R¹ is hydrogen or methyl, R² is C₁₋₆-alkyl or C₁₋₆-alkylsubstituted by C₁₋₆-alkoxy or aryloxy, R³ and R⁴ independently arehydrogen or C₁₋₆-alkyl, n is an integer >1, with the proviso that theweight average molecular weight of the polymer as measured bygel-permeation chromatography is between 3,000 and 50,000. 11.Poly-(1-methyl- 1-[2-(phenoxymethyl)-1,4,6-trioxaspiro[4.4]nonane-7-yl]methoxycarbonyl) ethylene having repeating units of theformula 4

and a weight average molecular weight in the range of 5,000 to 50,000 asmeasured by gel-permeation chromatography. 12.Poly-(1-methyl-1-[2-(phenoxymethyl)-1,4,6-trioxaspiro[4.4]nonane-7-yl]carbonyloxy-ethoxycarbonyl)ethylene having repeating units of the formula 8

and a weight average molecular weight in the range of 5,000 to 50,000 asmeasured by gel-permeation chromatography. 13.Poly(1-methyl-1-[2-(phenoxymethyl)-8,8-dimethyl- 1,4,6-trioxaspil-m ro[4.4]nonane-9-yl]oxycarbonyl) ethylene having repeating units of theformula 12

and a weight average molecular weight in the range of 5,000 to 50,000 asmeasured by gel-permeation chromatography.
 14. The polymer according toclaim 9, wherein the weight average molecular weight as measured by gelpermeation chromatography is between 500 and 500,000.
 15. The polymeraccording to claim 9, wherein the weight average molecular weight asmeasured by gel permeation chromatography is between 1000 and 50,000.16. The polymer according to claim 9, wherein the weight averagemolecular weight as measured by gel permeation chromatography isbetween25,000 and 45,000.